Anti-reflection film and process for preparation thereof

Abstract

This invention provides an anti-reflection film for use in various displays which prevents the reflection of light on the surface and enables necessary visual information to be clearly discerned. The anti-reflection film has a hard coat layer 4 , an intermediate refractive index layer 3 , a high refractive index layer 2 and a low refractive index layer 1 formed in this sequence on a transparent base film 5 , such that the refractive indices of the adjacent layers satisfy the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer >1.40.

What is claimed is:  
     
       1. An anti-reflection film having an intermediate refractive index layer, a high refractive index layer and a low refractive index layer formed in this order on a transparent base film through a hard coat layer, said anti-reflection film comprising: 
       the low refractive index layer comprising an SiO x  layer where x is 1.5 to 4.0;  
       the intermediate refractive index layer comprising a coating of a composition comprising a binder and ultrafine particles having a refractive index of 1.5 or more; and  
       the high refractive index layer; and  
       said anti-reflection film having:  
       the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer>1.40;  
       the thickness of each refractive index layer being 80 to 110 nm for the low refractive index layer, 30 to 110 nm for the high refractive index layer, and 50 to 100 nm for the intermediate refractive index layer; and  
       an optical film thickness D not larger than the wavelength of visible light (D=n·d wherein n is the refractive index of the intermediate refractive index layer and d is the thickness of the intermediate refractive index layer).  
     
     
       2. An anti-reflection film as claimed in claim  1 , wherein the hard coat layer has irregularities on its surface in contact with the intermediate refractive index layer. 
     
     
       3. An anti-reflection film as claimed in claim  1 , wherein the hard coat layer is provided on the transparent base film directly or through a primer layer and/or an adhesive layer. 
     
     
       4. An anti-reflection film as claimed in claim  1 , wherein the intermediate refractive index layer comprises 1 part by weight of a thermosetting resin and/or an ionizing radiation curing resin and 0.1 to 20 parts by weight of ultrafine particles of one or more kinds selected from the group consisting of ultra-fine particles of ZnO, TiO 2 , CeO 2 , Sb 2 O 5 , SnO 2 , ITO, Y 2 O 3 , La 2 O 3 , Al 2 O 3 , Hf 2 O 3  and ZrO 2 . 
     
     
       5. An anti-reflection film as claimed in claim  1 , wherein the high refractive index layer and the low refractive index layer are each a layer provided by vacuum coating. 
     
     
       6. An anti-reflection film as claimed in claim  1 , wherein the low refractive index layer is formed by plasma CVD involving the discharge of the starting gas of an organosiloxane, and the undecomposed organosiloxane remains in an amount of 0.1 to 0.2 parts of carbon based on one part of silicon. 
     
     
       7. An anti-reflection film as claimed in claim  1 , wherein an antifouling layer may be formed on the low refractive index layer. 
     
     
       8. An anti-reflection film having an intermediate refractive index layer, a high refractive index layer and a low refractive index layer formed in this order on a transparent base film through a hard coat layer, said anti-reflection film comprising: 
       the low refractive index layer comprising an SiO x  layer where x is 1.5 to 4.0;  
       the intermediate refractive index layer constituted by coating a paint comprising a binder and ultrafine particles having a refractive index of 1.5 or more; and  
       the high refractive index layer having electric conductivity; and  
       said anti-reflection film having:  
       the relationship 2.20>refractive index of the high refractive index layer>refractive index of the intermediate refractive index layer>refractive index of the low refractive index layer>1.40; and  
       the ultrafine particles of the intermediate refractive index layer comprising ZrO 2  particles.  
     
     
       9. An anti-reflection film as claimed in claim  1 , wherein the high refractive index layer has electric conductivity.